Well I may have found why my MH is not holding power in the coach batteries. I had refilled the two batteries (one coach, one truck) under the hood, but had neglected the two Trojan 6V under the bus. When I accessed them, and topped up the water, they took nearly four Litres of water between them (about 1 gallon). Now, for some strange reason, they don't seem to be holding their charge. Is there any way I can resurrect them, or do I just bite the bullet and start again with fresh ones? I think that the factory charger basically boiled them dry while plugged into shore power for three weeks without checking the water levels.

I need to get them mounted onto a slide system so that I can access them much more easily, and I need to double from two to four to give me more storage. I was thinking of buying four new matching batteries anyway - any advantage in that? Solar is also just around the corner too, and I am trying to plan how much I need to keep my charge up. As I see it, I want to calculate how many ampere/hours I intend to use each day, and plan for that to be about 25% of my total storage, and for there to be enough solar to boost around 35% of the total each day? This would mean that I would run the batteries above 70% charge and with a smart charger, keep them topped up at worst every second day.

My calculations should be Watts/12, times the expected running time each day for each appliance, and then total. What % should I factor in for losses in the inverter?

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Gracie
If the electrolyte level got below the lead plates, you'll have to install new batteries. I suggest the batteries to be the same. If your electrolyte level dropped that much in 3 weeks, I would check your charger's voltage to see if it is overcharging your batteries. Next, I'd invest in a battery water maintanance system that keeps the electrolyte levels in the batteries at their proper level. Very simple system since it's difficult for you to check those levels.
Also, to install a sliding battery tray takes some doing if it wasn't installed originally, thus my suggestion for the battery water maintenance system.
Solar power. I'd suggest to just check the numerous web sites that you would find doing a search for RV solar charging systems. Those sites would give you a lot of information of about what size panels you need, the type of charge controller you need as well as help on how to calculate your overall usage.
Enjoy your travels
Byron
Louisiana, USA

I am buying new batteries today and am tossing up between 6v Deep Cycle or 12V Gel. 1 x 12V gel will cost me NZ$550 for 110 AH, 2 x 6V will cost me NZ$600 for 220AH, but take up slightly less than twice the space. In other words I can get more 12V batteries in the space available, that will add up to more AH. I am leaning towards the gel batteries as it is very dificult to access the batteries under the coach and the gel hold their charge longer than the lead acid. The price is similar, and I not really worrying about doing it as cheaply as possible if I get better value by spending more. The lack of maintenance on the gel batteries REALLY appeals, is their lifetime similar to the lead-acid?

Apparently the gel batteries last much longer, so that makes the higher initial cost more appealing. I have put ONE 110AH gel battery in at present, but within two weeks will add at least one more and two 80 W solar panels with Power manager. This should allow me to at least park up the MH without plugging in to shore power. I need to modify the battery cage to hold up to 6 gel batteries, and will make the Solar expandable so that I can add more easily as I need to. Will keep you posted as to how I am going!
Cheers

Apparently the gel batteries last much longer, so that makes the higher initial cost more appealing. I have put ONE 110AH gel battery in at present, but within two weeks will add at least one more and two 80 W solar panels with Power manager. This should allow me to at least park up the MH without plugging in to shore power. I need to modify the battery cage to hold up to 6 gel batteries, and will make the Solar expandable so that I can add more easily as I need to. Will keep you posted as to how I am going!
Cheers

I hate to be a downer, but, you really need to replace all batteries at the same time. Batteries are funny animals. If you connect one new battery with old weak batteries, the old ones will act as a parasite on the new one. You could do harm to that one new battery.

Usually when the plates are exposed you have damaged / warped the plates due to overheating. The electrolyte actually keeps them cool.

The thing that kills wet cell batteries is called sulphation which is acid crystals building up on the plate blocking the charge from getting thru.

One proven technique to remove or prevent sulphation is epsom salts. l/4 to 1/2 teaspoon to each cell. Charge at 5 amps max for 24 hours and then check cells for bubbling. If any cell fail to bubble, add another dose to that cell and charge for twelve more hours. If no bubbling, trash the battery.

Use a load tester to check the battery, do not trust a hydrometer.

I add water once a year (good charging system) and a dose of epsom salts, same batteries that came in my coach, purchased used 5 years ago.

Thanks Vegasdan - I will buying three of the extra batteries before Xmas so they will only be a couple of months apart, if that. The extra two will be before March next year, so they should be close enough, but thanks for the heads up.

Thanks also trpwire - I suspect that I may have been able to resurrect the batteries if I had got to them earlier, as they were Trojan 105's, but they had started to bulge at the sides when I took them out, so as Vegasdan said, "they are toast".

One advantage I didn't realise to the gel batteries is that they are slightly lower in profile, so that IF I do have to maintain them, access will be easier. Should be easier to at least keep terminals clean!

I put 1/4" mineral oil in ALL my batteries, and add water twice per year. YEP, still have the original deep cycle 6V batteries since 03. The oil is not a secret fluid, it jest keeps the water from evaporating when the battery is being charge. When the bubble is popping out, it goes in the oil and water stays behind and oil the covering the bubble. Which means very little water moisture lost. Been using ths for 5 years now, and no problems. Do a search and find out for your self. Good Luck........